It is often desirable to remove deposits from a substrate in order to clean the substrate. For example, U.K. Patent No. 2,172,304 (Tsukada) discloses a composition used to remove thermoplastic resins and residues such as acetal and thermoplastic polyesters resins. Generally, acetal and thermoplastic polyester resins are used as materials in molding processes such as injection molding to form objects such as steam iron housings, automotive electrical switches and television cathode-ray tube sockets. Tsukada's preferred composition comprises a .beta.-, .gamma.- or .delta.-lactone mixed with an alcohol. Tsukada also mentions that the lactones can be mixed with an ester, in particular ethyl acetate, instead of an alcohol.
In addition for the need to remove acetal and thermoplastic polyesters resins and their residues, there is a need to remove paints and/or coatings from a substrate for a variety of reasons such as repainting or refinishing the substrate. Paints and/or coatings include conventional paints, varnishes, enamels, lacquers, water emulsion finishes and non-aqueous dispersions. The term "coating" hereinafter applies to both paints and coatings.
Coatings can be removed in a number of different ways. For example, they can be physically removed by use of a scraper or power sander or they can be chemically removed. However, methods utilizing chemical compositions have achieved considerable popularity because they are much easier to use than the non-chemical alternatives.
The chemical compositions used to remove coatings broadly fall within three general classes: (1) the alkali or acid class, (2) the organic solvent class and (3) the waterbased class. The first class generally comprises alkalis or acids which attack the coating by the chemical action of the ingredients thereof. Representative examples of this class are described in U.S. Pat. Nos. 3,681,250, 3,615,825 and 3,972,839. These alkali or acid compositions are undesirable because they often exhibit deleterious effects on wood or because they require considerable after treatment to insure the compositions complete removal from the treated surface.
The second class of chemical compositions used to remove coatings generally comprises solvent based compositions which rely upon the solvent power of the composition to dissolve or at least soften the coating. Representative examples of compositions of the second class include aromatic hydrocarbons, lower aliphatic esters, ketones, alcohols, chlorinated solvents such as methylene chloride or similar organic solvents. Many of the lower molecular weight solvents are undesirable because they are too volatile and thus, readily evaporate once applied to the surface. Other solvents are highly flammable thereby posing handling and shipping problems. In addition to posing application and handling problems, some of these organic solvents are undesirable because of their adverse effects upon the atmosphere and their toxicity.
Therefore, attempts have been made to overcome some of the problems associated with the solvent based compositions. Higher molecular weight solvents including higher aliphatic esters have been used to overcome some of the problems associated with the lower molecular weight solvents. For example, U.S. Pat. No. 4,120,810 (Palmer) discloses a paint remover which comprises an aromatic hydrocarbon and a second component which can include n-methyl-2-pyrrolidone or chemical analogs thereof, diacetone alcohol, or butyrolactone. U.S. Pat. No. 4,508,634 (Elepano et al.) teaches the use of a composition suitable for removing paint from skin comprising propylene carbonate, at least one organic cosolvent, at least one thickening agent, at least one buffering agent, at least one surfactant and water. U.S. Pat. No. 4,780,235 (Jackson) teaches the use of a paint remover which comprises (a) at least one C.sub.1 -C.sub.4 dialkyl ester of a C.sub.4 -C.sub.6 aliphatic ester, (b) an activator, (c) a surfactant and (d) at least one nonhalogen containing organic solvent such as N-methyl-2-pyrrolidone. U.S. Pat. No. 5,030,290 (Davis) teaches the use of a paint stripper comprising (a) a high molecular weight polymeric resin such as polyvinyl formal resin, (2) a plasticizer such as a dibasic ester and (3) a solvent which can be butyrolactone. U.S. Pat. No. 5,035,829 (Suwala) teaches the use of paint removing comprising an organic acid, an alkylene glycol and a .gamma.-lactam or .gamma.-lactone. While the Palmer, Davis and Suwala compositions have overcome some of the problems associated with the second class of removers, these compositions have either not been as effective as the solvent based paint and/or coating removers or have retained some of the adverse effects of the solvent based systems.
The third class of chemical compositions used to remove coatings generally comprises waterbased systems. An example of such a system is U.S. Pat. No. 4,927,556 (Pokorny) which discloses the use of a composition used to remove coatings from surfaces consisting essentially of water, at least one dibasic ester and at least one water soluble thickening agent. Although eliminating many of the problems associated with solvents such as toxicity, the Pokorny composition did not perform as fast as solvent based systems.
Thus, there currently exists a need for a coating remover which is fast and effective and yet, does not exhibit many of the adverse effects associated with alkali or solvent based compositions.